The present invention relates to a work-cutting device, such as a right-angle shearing machine, for cutting a work, formed, for example, of sheet metal, using a fixed lower cutting edge and a movable upper cutting edge.
A conventional work-cutting device is comprised of a right-angle shearing machine for using an L-shaped fixed lower cutting edge 42 and a movable upper cutting edge 41 extending along the inside of the lower cutting edge to cut a work W along a right angle direction P to obtain a rectangular piece Wb, as shown in FIG. 12.
In such a work-cutting device, the upper cutting edge 41 is subjected to a reaction force F from the work W which is applied upon cutting in a direction reverse to that of a cutting pressure, as shown in FIG. 14. A lateral load Fa, a horizontal component of the reaction force F, flexes the upper cutting edge 41 and its support system to cause the upper cutting edge 41 to escape in a lateral direction of the work-cutting device, thereby widening the clearance between the upper and lower cutting edges 41, 42. That is, during lowering, the upper cutting edge 41 follows an upper-cutting-edge locus b that is laterally offset from an inherent upper-cutting-edge locus a, which is shown by the chain line in FIG. 13. The amount of offset A between the loci a and b becomes maximum at a point of time during lowering when the cutting pressure is highest. A cut surface of the work W is located so as to correspond to the offset locus b.
Subsequently, once cutting has been finished, the lateral load Fa is eliminated to cancel the displacement of the upper cutting edge 41, which thus elevate whiles following the inherent upper-cutting-edge locus a. At this point, since the cut surface of the work W is offset along the locus b of the upper cutting edge 41 which has been actually followed during lowering, the upper cutting edge 41 elevates while rubbing the cut surface of the work W hard. This rubbing wears the upper cutting edge 41 to reduce its lifetime.
Although a work-cutting device for adjusting the clearance between the upper and lower cutting edges during work cutting has been proposed by the applicant (for example, Japanese Patent Application No. 9-172260 (Unexamined Japanese Patent Application Publication No. 11-10437)), it does not take into account the prevention of possible rubbing during the elevation of the upper cutting edge.
It is an object of the present invention to provide a work-cutting device that can ease possible rubbing between the upper cutting edge and the cut work surface during the elevation of the upper cutting edge to prevent the upper cutting edge from being worn in order to increase its lifetime and that can avoid a possible upward warp of the work to maintain the processing quality.
It is another object of the present invention to enable possible rubbing during the elevation of the upper cutting edge to be prevented using simple control.
It is yet another object of the present invention to enable possible rubbing during the elevation of the upper cutting edge to be prevented using a simple control even if the upper and lower cutting edges are L-shaped.
An embodiment of the present invention will be described with reference to FIG. 8, which corresponds to a preferred embodiment. This is a work-cutting device for elevating and lowering a movable upper cutting edge 12 relative to a fixed lower cutting edge 13, thereby cutting a work W, wherein the device has an upper-cutting-edge tight-contact avoidance means 10 for widening the clearance between the upper cutting edge 12 and a work cutting surface after work cutting has been finished.
According to this construction, after the completion of the work cutting, the upper-cutting-edge tight-contact avoidance means 10 widens the clearance between the upper cutting edge 12 and the work cutting surface, and the upper cutting edge 12 elevate with the clearance kept widened. Thus, even if the cutting surface is offset from the lower cutting edge 13 in a direction in which it leaves the lower cutting edge 13, due to the escape of the upper cutting edge 12 upon cutting, the upper cutting edge 12 is prevented from being forced against the cut work surface during the elevation of the upper cutting edge 12. Accordingly, the upper cutting edge 12 is prevented from being worn and thus has a long lifetime. In addition, a possible upward warp of the work W can be avoided to maintain the processing quality. To widen the clearance between the upper cutting edge 12 and the cut work surface after the completion of work cutting, the upper cutting edge may be moved so as to widen the clearance between the upper cutting edge 12 and the lower cutting edge 13, or the position of the work may be adjusted without the adjustment of clearance.
According to the present invention, the upper-cutting-edge tight-contact avoidance means 10 comprises a clearance adjustment mechanism 22 for adjusting the clearance between the upper cutting edge 12 and the lower cutting edge 13, an adjustment drive source 25 for driving this clearance adjustment mechanism 22, and a clearance control means 35 for allowing the clearance adjustment mechanism 35 to widen the clearance between the upper cutting edge 12 and the lower cutting edge 13 after the completion of work cutting and before the elevation of the upper cutting edge 12. The clearance adjustment mechanism 22 is comprised, for example, of an eccentric cam mechanism.
With this construction, simply by setting adjustment mechanism 22 for use in adjusting control means 35 using the clearance adjustment mechanism 22 for use in adjusting the clearance during cutting, as well as the adjustment drive mechanism 25, the clearance can be widened after the completion of work cutting and before the elevation of the upper cutting edge, and possible rubbing can be prevented during the elevation of the upper cutting edge, using a simple control.
According to the present invention, the lower cutting edge 13 may have a generally L-shaped planar shape, and the upper cutting edge 12 may have a generally L-shaped planar shape extending along the lower cutting edge 13. The clearance adjustment mechanism 22 adjusts the clearance in an oblique direction relative to the two sides of each of the lower cutting edge 13 and the upper cutting edge 12 which form the L shape.
A work-cutting device with the generally L-shaped upper cutting edge 12 and the lower cutting edge 13 is referred to as a xe2x80x9cright-angle shearing machinexe2x80x9d and is generally used for cutting the work W in its corner into a rectangular piece Wb. In such a work-cutting device, if the clearance adjustment mechanism 22 adjusts the clearance in the oblique direction as described above, the two sides of the upper cutting edge 12 which form an L shape can simultaneously be subjected to clearance adjustments, thereby preventing possible abrasion of the upper cutting edge associated with its elevation, using the simple construction.
According to the present invention, the clearance control means 35 may adjust the clearance depending on the thickness of the work W while the upper cutting edge 12 is lowered during work cutting, and may adjust the clearance, during the elevation of the upper cutting edge, to a value larger than that during lowering.
In addition to the present invention, the clearance adjustment mechanism 22 includes means 21 for moving the position of the upper cutting edge 12 in a horizontal direction and an adjustment drive source 25 for driving the means 21.